Hard drives, which store data on tape, magnetic discs, optical disks, etc., have become increasingly important with the rise in electronic data storage, as seen, for example, in consumer photo, video, and music applications. However, hard drives have long suffered, and continue to suffer, from vibration-related errors.
Vibration-related errors occur when components of the hard drive shake, or are otherwise disturbed. Vibration can be attributed to many different sources, such as external movement of the entire hard drive. Large external vibrations, which are difficult to control, often lead to hard errors, which are major faults from which the hard drive cannot recover without user intervention. More common, however, are relatively smaller vibrations which often lead to soft errors from which the hard drive will attempt to recover without user intervention. Typical soft errors include a disc reading/writing element of the hard drive being unable to lock onto a track in a disc, more commonly known as “skipping.”
Vibrations leading to soft errors may originate from several sources, including the natural vibration of moving electrical components. For example, the natural vibrations caused by spinning fan blades and by the movement of recordable media, such as spinning discs, are known to cause soft errors. Moreover, hard drives are often housed alongside other hard drives and other moving components, whose normal operating vibrations are known to cause vibrations in neighboring hard drives.
The problem of soft errors due to the normal operating vibration of moving electrical components is amplified when components vibrate in synchronization. That is, moving components may vibrate at different frequencies depending on several factors, such as the speed at which the component is moving. When multiple components begin vibrating in synchronization, that is, at or near the same frequency, the potential for soft errors is exacerbated. For example, skipping occurs more often when the actuator arm and the chassis of a hard drive vibrate at the same frequency.
While problems caused by vibration have been known for some time, they are more pronounced with later generation hard drives, because components move at faster rates than in earlier hard drives. For example, cooling fans and spinning recordable media in today's systems have much higher revolutions per minute (RPM), as compared to older components. Manufacturers have attempted to deal with the problem of vibration by testing individual hard drives on shaker tables before they are released to consumers. Structural changes are made to hard drives when vibration-related errors are identified in this testing environment.
Current vibration testing in hard drives, however, often leads to lost time and revenue associated with warranties provided by manufacturers. This is because consumers experiencing vibration-related errors return hard drives to manufacturers to correct problems, such as excessive skipping. However, even though manufacturers run the hard drives through a series of diagnostic tests, they are unable to replicate the consumer's working environment. Thus, manufacturers attempting to honor product warranties often cannot duplicate or fix the problems experienced by the consumers.